JP2006-336845A discloses a hybrid construction machine in which an engine and a rotary shaft of a main pump are linked via a clutch and a rotational force of the rotary shaft is transmitted to a motor generator via a power transmission device.
The motor generator is connected to a regenerative hydraulic motor in a system different from the engine via a clutch. Accordingly, the motor generator can fulfill a power generation function utilizing either an output of the engine or an output of the regenerative hydraulic motor.